Prospects for Developing Odour Baits To Control Glossina fuscipes spp., the Major Vector of Human African Trypanosomiasis

Abstract

We are attempting to develop cost-effective control methods for the important vector of sleeping sickness, Glossina fuscipes spp. Responses of the tsetse flies Glossina fuscipes fuscipes (in Kenya) and G. f. quanzensis (in Democratic Republic of Congo) to natural host odours are reported. Arrangements of electric nets were used to assess the effect of cattle-, human- and pig-odour on (1) the numbers of tsetse attracted to the odour source and (2) the proportion of flies that landed on a black target (1×1 m). In addition responses to monitor lizard (Varanus niloticus) were assessed in Kenya. The effects of all four odours on the proportion of tsetse that entered a biconical trap were also determined. Sources of natural host odour were produced by placing live hosts in a tent or metal hut (volumes≈16 m3) from which the air was exhausted at ∼2000 L/min. Odours from cattle, pigs and humans had no significant effect on attraction of G. f. fuscipes but lizard odour doubled the catch (P<0.05). Similarly, mammalian odours had no significant effect on landing or trap entry whereas lizard odour increased these responses significantly: landing responses increased significantly by 22% for males and 10% for females; the increase in trap efficiency was relatively slight (5–10%) and not always significant. For G. f. quanzensis, only pig odour had a consistent effect, doubling the catch of females attracted to the source and increasing the landing response for females by ∼15%. Dispensing CO2 at doses equivalent to natural hosts suggested that the response of G. f. fuscipes to lizard odour was not due to CO2. For G. f. quanzensis, pig odour and CO2 attracted similar numbers of tsetse, but CO2 had no material effect on the landing response. The results suggest that identifying kairomones present in lizard odour for G. f. fuscipes and pig odour for G. f. quanzensis may improve the performance of targets for controlling these species.

Onchocerciasis transmission in Ghana: biting and parous rates of host-seeking sibling species of the Simulium damnosum complex

“…[49][50][51] and mosquito [52] collections, were trialled as potential replacements of vector collector methods. These traps were used for blackfly collection on sporadic dry days during the rainy season in 2009 and followed up with a full feasibility investigation during a two-week period in August 2010 in the dry season.…”

Olfaction in vector-host interactions

“…It is therefore pertinent to summarise briefly the main features of the important Palpalis group species (reviewed in Solano et al 2009). …”

“…Finally, in Congo-Brazzaville, Frezil and Carnevale (1976) showed that baiting a trap with carbon dioxide increased the catch of G. f. quanzensis Pires ~40×. (Omolo et al 2009, Rayaisse et al 2010 suggest that these species show moderate but significant responses to host odours. For instance, studies in Burkina Faso have shown that there is a significant ~1.5× increase in the numbers of G. p. gambiensis attracted to a source of ox odour, and that a blend of acetone, 4-methylphenol, 3-n-propylphenol and octenol can double the catch from traps (IAEA 2003, Rayaisse et al 2010.…”

“…For instance, studies in Burkina Faso have shown that there is a significant ~1.5× increase in the numbers of G. p. gambiensis attracted to a source of ox odour, and that a blend of acetone, 4-methylphenol, 3-n-propylphenol and octenol can double the catch from traps (IAEA 2003, Rayaisse et al 2010. Studies of G. fuscipes species (Omolo et al 2009) confirm that G. f. fuscipes responds to odours from lizard but not to those from cattle, humans or pigs whereas G. f. quanzensis appears to show significant responses to pig odours. The absence of any significant response by G. f. fuscipes to cattle odour is particularly intriguing since some experiments showed that even the odour from four cattle, which would have contained ~8 l/min of carbon dioxide, was ineffective.…”

Kairomones - important substances in interspecific communication in vertebrates: a review

“…Omolo et al (2009) have studied the responses of this insect to natural host odours by odour baits. Odours of cattle, pig, human and monitor lizard (Varanus niloticus) were used in the experiments.…”